Research On Batch Preparation Technology Of Diamond Heat Dissipation Materials

With the rapid advancement of electronic components,integrated circuits,and semiconductors,the internal heat flux density continues to increase,which seriously affects device performance.Consequently,there is an increased demand for improved heat dissipation performance in devices.Diamond possesses excellent properties,such as low density,high thermal conductivity,low thermal expansion coefficient,and electrochemical stability,making it an ideal heat dissipation material.The hot filament chemical vapor deposition(HFCVD)method has gained widespread use in diamond preparation,owing to its simple equipment,controllable process parameters,and ability to achieve large-area deposition.However,the HFCVD method exhibits a lower growth rate and higher energy consumption,leading to higher production costs and reduced efficiency,compared to traditional copper-based heat dissipation materials.Thus,increasing the diamond growth rate and decreasing the energy consumption of the equipment are critical challenges to be urgently addressed to reduce the productions costs of diamond heat dissipation materials.In this present study,Computational Fluid Dynamics(CFD)simulation was applied to simulate the temperature field inside diamond equipment,with the aim of improving temperature field uniformity and reducing energy consumption by using specialized structures such as heat shield structures.Upon small-scale HFCVD production equipment,the high-efficiency and high-quality deposition processes of diamond on substrate surfaces were explored,enabling the transition to large-scale diamond deposition.Furthermore,a novel process for batch preparation of self-standing diamond via HFCVD was proposed and the growth rate,film quality,surface morphology,and roughness of the diamond were characterized by scanning electron microscopy(SEM),Raman spectroscopy,and laser scanning confocal microscopy(LSCM).The primary research contents of this study include:Studies were conducted on the diamond growth process parameters as well as the substrates used for self-standing diamond film growth.The effects of key parameters such as methane concentration,hot filament power,chamber pressure,and substrate type on diamond growth rate and quality were investigated.The results reveal that suitable power is crucial for diamond growth,with the ideal power for small-scale production being1600 W.Surface morphology of the diamond is jointly determined by carbon source concentration and chamber pressure,with the optimal parameters being a carbon source concentration of 18/300 sccm during nucleation stage and 14/300 sccm during growth stage,along with a chamber pressure of 4000 Pa(for microcrystalline diamond)and 2000 Pa(for nanocrystalline diamond).Furthermore,silicon carbide serves as an effective substrate for self-standing diamond growth that can guarantee the integrity of the film.Using CFD simulation software,the temperature filed inside a smallscale HFCVD equipment was simulated,taking into account three heat transfer mechanisms: thermal conduction,thermal radiation,and thermal convection.The components and layout of the HFCVD system were optimized to achieve improved temperature field uniformity and energyefficiency utilization.The simulation results indicate that the use of quartz sample holders and heat shield structures can reduce energy losses by approximately 30%.To validate the accuracy and reliability of the simulation method,real-time temperature measurement devices were integrated into the equipment,demonstrating the accuracy of the simulation results.Furthermore,the vacuum reaction chamber was enlarged,and the arrangement of the hot filaments and substrates was optimized to establish a large-scale simulation model for diamond growth using HFCVD.A series of analyses were performed to determine the temperature distribution of the substrate inside the chamber.It is found that the spacing,height,diameter,and temperature of the hot filament were supposed to set to 22 mm,8 mm,0.6 mm,and 2200 °С,respectively.As a result,the temperature uniformity of the substrate was improved and was within the appropriate range for the diamond deposition.Finally,a novel method was proposed for fabricating batch selfstanding diamond heat sinks by utilizing silicon carbide as the substrate,in conjunction with HFCVD,mechanical polishing,and laser cutting techniques.Multi-layer diamond is deposited on the surface of silicon carbide by HFCVD method repeatedly until achieving the desired thickness.The surface of the diamond coating is subsequently mechanically polished,and he silicon carbide substrate is then cut by laser processing technology to complete the initial stripping process.The surface exposed after cutting is further mechanically polished to obtain highquality double-sided polished self-standing diamond heat sinks with the roughness of less than 200 nm on both sides.